1. Field of the Invention
The present invention relates to an intro-subject introduction apparatus which is introduced into the inside of a subject, moves within the inside of the subject, and acquires intra-subject information, an extracorporeal receiving apparatus which is arranged outside the subject and acquires intra-subject information acquired by the intro-subject introduction apparatus, and an intra-subject information gathering system including these apparatuses.
2. Description of the Related Art
At present, a deglutition type endoscope, i.e., a so-called capsule type endoscope (intro-subject introduction apparatus) is put to practical use in the field of endoscopy. Such a capsule type endoscope is provided with an imaging function and a wireless communication function. Further, the capsule type endoscope, after it is swallowed from a mouth of a subject for the purpose of observation (examination) until it is naturally excreted from the body of the subject, moves through the inside of a body cavity, i.e., through the inside of internal organs such as a stomach and small intestine in accordance with the peristaltic movement and performs imaging.
Image data items imaged by the capsule type endoscope in the body of the subject while the endoscope moves through the body cavity are transmitted in sequence to the extracorporeal receiving apparatus provided outside the subject by wireless communication, and stored in a memory provided externally via the extracorporeal receiving apparatus. By carrying such an extracorporeal receiving apparatus having a wireless communication function and memory function with the subject, the subject can freely move after the subject swallows the capsule type endoscope until the capsule is excreted from the body of the subject.
As one of wireless communication systems in the capsule type endoscope, a human body communication system is proposed in which a subject is utilized as a signal transmission medium so as to transmit image data to the outside of the subject. For example, in a human body communication system proposed in International Publication No. 2004/068748, two electrodes for signal transmission are provided on an outer surface of a capsule type endoscope. A potential difference corresponding to image data is generated between signal transmitting electrodes, thereby causing an electric current to flow from the inside of a subject to the outside of the subject. Further, the current is detected by receiving electrodes of an extracorporeal receiving apparatus arranged outside the subject. As a result, it becomes possible to transmit image data by utilizing a human body as a signal transmission medium.
Here, a conventional intra-subject information gathering system utilizing a human body communication system has a problem of a lack of stability in communication. The conventional intra-subject information gathering system utilizing a human body communication system has a configuration in which transmitting electrodes are arranged on the outer surface of the capsule type endoscope. Since the capsule type endoscope having such a configuration moves through the inside of the subject, there is therefore a possibility that the condition of contact between the transmitting electrodes and the inside of the subject changes. If the condition of contact between the transmitting electrodes of the capsule type endoscope and the inside of the subject changes, the output impedance viewed from the transmitting electrodes also changes. As a result, a mismatch is caused between the transmitting electrodes and the subject with respect to the impedance variation amount. Further, there is a possibility of a phenomenon in which loss of transmission signal power of the capsule type endoscope is caused being brought about.
In the conventional capsule type endoscope, a control method for the output impedance variation amount resulting from the contact condition of the transmitting electrodes is not taken into consideration. Accordingly, it is conceivable that the loss of the transmission signal power brings about lowering of the received signal level and liability to an influence of noise, and therefore that the intra-subject information gathering system cannot deal with maintenance of communication stability.